Synthetic lubricant base stocks having an improved pour point

ABSTRACT

Synthetic lubricant base stocks having a low pour point are disclosed. These synthetic lubricant base stocks comprise a mixture of (1) oligomers prepared from a linear olefin having from 10 to 24 carbon atoms; and (2) alkylated decalin having an alkyl group containing from 10 to 24 carbon atoms. These synthetic lubricant base stocks may be prepared by hydrogenating the co-reaction products of a linear olefin having from 10 to 24 carbon atoms and naphthalene.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is related to co-pending U.S. patent application Ser.No. 07/500,631, filed Mar. 28, 1990, which relates to the preparation ofsynthetic lubricant base stocks by oligomerizing linear olefins by meansof certain acidic montmorillonite clays, and to co-pending U.S. patentapplication Ser. No. 07/516,931, filed Apr. 30, 1990, which relates tothe preparation of synthetic lubricant base stocks by oligomerizingcertain mixtures of internal and alpha-olefins by means of certainacidic montmorillonite clays. This application also relates toco-pending U.S. patent application Ser. No. 07/516,870, filed Apr. 30,1990, which relates to synthetic lubricant base stocks made byoligomerizing linear olefins by means of certain aluminumnitrate-treated acidic montmorillonite clays, and to co-pending U.S.patent application Ser. No. 07/522,941, filed May 14, 1990, whichrelates to the preparation of synthetic lubricant base stocks byco-oligomerizing propylene and long-chain alpha-olefins by means ofcertain acidic montmorillonite clay catalysts. This application alsorelates to co-pending U.S. patent application Ser. No. 07/525,807, filedMay 21, 1990, which concerns synthetic lubricant base stocks made byco-oligomerizing 1,3-di-isopropenyl benzene and long-chain alpha-olefinsby means of certain acidic montmorillonite. The totality of each ofthese previously filed applications is incorporated herein by reference.clay catalysts. The totality of each of these previously filedapplications is incorporated herein by reference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to synthetic lubricant base stocks, and moreparticularly to synthetic lubricant base stocks having a low pour point.

2. Description of Related Methods

Synthetic lubricants are prepared from man-made base stocks havinguniform molecular structures and, therefore, well-defined propertiesthat can be tailored to specific applications. Mineral oil base stocks,on the other hand, are prepared from crude oil and consist of complexmixtures of naturally occurring hydrocarbons. The higher degree ofuniformity found in synthetic lubricants generally results in superiorperformance properties. For example, synthetic lubricants arecharacterized by excellent thermal stability. As automobile engines arereduced in size to save weight and fuel, they run at highertemperatures, therefore requiring a more thermally stable oil. Becauselubricants made from synthetic base stocks have such properties asexcellent oxidative/thermal stability, very low volatility, and goodviscosity indices over a wide range of temperatures, they offer betterlubrication and permit longer drain intervals, with less oilvaporization loss between oil changes.

Synthetic base stocks may be prepared by oligomerizing internal andalpha-olefin monomers to form a mixture of dimers, trimers, tetramersand pentamers with minimal amounts of higher oligomers. The unsaturatedoligomer products are then hydrogenated to improve their oxidativestability, with little change in other properties. The resultingsynthetic base stocks have uniform isoparaffinic hydrocarbon structuressimilar to high quality paraffinic mineral base stocks, but have thesuperior properties mentioned due to their higher degree of uniformity.

Synthetic base stocks are produced in a broad range of viscosity grades.It is common practice to classify the base stocks by their viscosities,measured in centistokes (cSt) at 100° C. Those base stocks withviscosities less than or equal to about 4 cSt are commonly referred toas "low viscosity" base stocks, whereas base stocks having a viscosityin the range of around 40 to 100 cSt are commonly referred to as "highviscosity" base stocks. Base stocks having a viscosity of about 4 toabout 8 cSt are referred to as "medium viscosity" base stocks. The lowviscosity base stocks generally are recommended for low temperatureapplications. Higher temperature applications, suHx as motor oils,automatic transmission fluids, turbine lubricants, and other industriallubricants, generally require higher viscosities, such as those providedby medium viscosity base stocks (i.e. 4 to 8 cSt grades). High viscositybase stocks are used in gear oils and as blending stocks.

The viscosity of the base stocks generally is determined by the lengthof the oligomer molecules formed during the oligomerization reaction.The degree of oligomerization is affected by the catalyst and reactionconditions employed during the oligomerization reaction. The length ofthe carbon chain of the monomer starting material also has a directinfluence on the properties of the oligomer products. Fluids preparedfrom short-chain monomers tend to have low pour points and moderatelylow viscosity indices, whereas fluids prepared from long-chain monomerstend to have moderately low pour points and higher viscosity indices.Oligomers prepared from long-chain monomers generally are more suitablethan those prepared from shorter-chain monomers for use as mediumviscosity synthetic lubricant base stocks.

One known approach to oligomerizing long-chain olefins to preparesynthetic lubricant base stocks is to contact the olefin with borontrifluoride together with a promotor at a reaction temperaturesufficient to effect oligomerization of the olefin. See, for example,co-assigned U.S. Pat. Nos. 4,400,565; 4,420,646; 4,420,647; and4,434,308. However, boron trifluoride gas (BF₃) is a pulmonary irritant,and breathing the gas or fumes formed by hydration of the gas withatmospheric moisture poses hazards preferably avoided. Additionally, thedisposal/neutralization of BF₃ raises environmental concerns. Thus, amethod for oligomerizing long-chain olefins using a non-hazardous,non-polluting catalyst would be a substantial improvement in the art.

Kuliev et al. attempted to prepare synthetic lubricants by oligomerizinglong-chain (C₉ -C₁₄) olefins using non-hazardous and non-pollutingacidic clays comprising sulfuric and hydrochloric acid-activatedbentonites from the Azerbaidzhan SSR. See Kuliev, Abasova, Gasanova,Kotlyarevskaya, and Valiev, "Preparation of High-Viscosity SyntheticLubricants Using an Aluminosilicate Catalyst," Institute ofPetrochemical Processes of the Academy of Sciences of the AzerbaidzhanSSR, Azer. Neft. Khoz., 1983, No. 4, pages 40-43. However, Kuliev et al.concluded that "it was not possible to prepare viscous or high-viscosityoils by olefin polymerization over an aluminosilicate catalyst" and that"hydrogen redistribution reactions predominate with formation ofaromatic hydrocarbon, coke, and paraffinic hydrocarbon." Gregory et al.,on the other hand, used Wyoming bentonite to oligomerize shorter-chainolefins. (See U.S. Pat. No. 4,531,014.) However, like Kuliev et al.,they also were unable to obtain a product high in dimer, trimer andtetramer, and low in disproportionation products.

Applicants discovered that it is possible to prepare synthetic lubricantbase stocks in good yield by oligomerizing long-chain olefins usingcertain acidic montmorillonite clay catalysts. Applicants found that ahigh conversion of long-chain olefin to dimer, trimer, and tetramer maybe obtained with formation of very little concomitant hydrogenredistribution by-product by using an acidic calcium montmorilloniteclay having a moisture content ranging up to about 20 wt.%, a residualacidity in the range of about 3 to about 30 mg KOH/g (when titrated to aphenolphthalein end point), and a surface area of about 300 M² /g orgreater. In addition to being excellent catalysts, these clays arenon-hazardous and non-polluting.

The viscosity of base stocks prepared in this manner may be improved byco-reacting long-chain linear olefins and naphthalene in the presence ofthese acidic montmorillonite catalysts. The resulting mixtures ofoligomers and alkylated naphthalenes exhibit a viscosity substantiallyhigher than that observed in base stocks comprising the olefin oligomersalone. Additionally, incorporating the naphthalene lowers the cost ofproducing the base stocks by replacing a portion of the more expensivelong-chain olefin feed with naphthalene. Dressler et al. (see U.S. Pat.No. 4,604,491, incorporated herein by reference) have alkylatednaphthalene with long-chain linear olefins in the presence of acidicmontmorillonite clay catalysts to prepare synthetic lubricant basestocks comprising mixtures of mono-alkylated and polyalkylatednaphthalenes. Applicants have discovered, surprisingly, that mixtures ofalkylated Decalins and olefin oligomers also provide synthetic lubricantbase stocks having an improved viscosity, but that have a lower pourpoint than those obtained from mixtures containing alkylatednaphthalenes.

SUMMARY OF THE INVENTION

In accordance with certain of its aspects, the invention relates to asynthetic lubricant base stock having a low pour point, comprising amixture of (1) oligomers prepared from a linear olefin having from 10 to24 carbon atoms; and (2) alkylated Decalin having an alkyl groupcontaining from 10 to 24 carbon atoms. In accordance with other of itsaspects, the invention relates to a process for preparing syntheticlubricant base stocks having a low pour point, comprising the steps of(1) co-reacting naphthalene and a linear olefin having from 10 to 24carbon atoms in the presence of an acidic montmorillonite clay; and (2)hydrogenating the resulting mixture of olefin oligomers and alkylatednaphthalenes, to obtain a mixture of reduced olefin oligomers andalkylated decalins.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Applicants have discovered certain synthetic lubricant base stockshaving a low pour point, comprising a mixture of (1) oligomers preparedfrom a linear olefin having from 10 to 24 carbon atoms; and (2)alkylated Decalin having an alkyl group containing from 10 to 24 carbonatoms. Synthetic lubricant base stocks may be prepared in good yield byoligomerizing long-chain linear olefins using certain acidicmontmorillonite clay catalysts. The viscosity of these base stocks isimproved when the starting materials comprise a mixture of long-chainlinear olefin and naphthalene, preferably from about 1 to about 40 wt.%naphthalene (i.e. in a weight ratio of naphthalene to linear olefin ofabout 1:99 to about 2:3.) More preferably, the mixture of long-chainlinear olefin and naphthalene contains from about 5 to about 25 wt.%naphthalene (i.e. in a weight ratio of naphthalene to linear olefin ofabout 1:20 to about 1:4.) Co-reacting the naphthalene and linear olefinfeed produces a mixture of olefin oligomers and alkylated naphthalenes.Applicants have discovered that synthetic lubricant base stocks having alower pour point may be obtained by saturating all double bonds presentin the oligomers and alkylated naphthalenes contained in the mixture,via catalytic hydrogenation, to obtain a mixture of reduced oligomersand alkylated Decalins. A modest increase in viscosity overnon-hydrogenated mixtures is observed as well. Preferably, the resultingbase stocks contain from about 1 to about 80 wt.% alkylated Decalin.More preferably, the resulting base stocks contain from about 5 to about40 wt.% alkylated Decalin.

Olefin monomer feed stocks useful in the present invention includecompounds comprising (1) alpha-olefins having the formula R"CH═CH₂,where R" is an alkyl radical of 8 to 22 carbon atoms, and (2) internalolefins having the formula RCH═CHR', where R and R' are the same ordifferent alkyl radicals of 1 to 20 carbon atoms, provided that thetotal number of carbon atoms in any one olefin shall be within the rangeof 10 to 24, inclusive. A preferred range for the total number of carbonatoms in any one olefin molecule is 12 to 18, inclusive, with anespecially preferred range being 13 to 16, inclusive. Mixtures ofinternal and alpha-olefins may be used, as well as mixtures of olefinshaving different numbers of carbon atoms, provided that the total numberof carbon atoms in any one olefin shall be within the range of 10 to 24,inclusive. The alpha and internal-olefins and naphthalene useful in thepresent invention may be obtained by processes well-known to thoseskilled in the art and are commercially available.

Oligomerization of linear olefins may be represented by the followinggeneral equation: ##STR1## where n represents moles of monomer and mrepresents the number of carbon atoms in the monomer. Thus,oligomerization of 1-decene may be represented as follows: ##STR2##

The reactions occur sequentially. Initially, olefin monomer reacts witholefin monomer to form dimers. The dimers that are formed then reactwith additional olefin monomer to form trimers, and so on. This resultsin an oligomer product distribution that varies with reaction time. Asthe reaction time increases, the olefin monomer conversion increases,and the selectivities for the heavier oligomers increase. Generally,each resulting oligomer contains one double bond.

The mono-alkylation of naphthalene by a linear olefin may be representedas follows: ##STR3## where m=number of carbon atoms in the olefinmonomer. Depending on the mole ratio of linear olefin to naphthalene andreaction conditions, poly-alkylation of the naphthalene also will occur.The alkylation of naphthalene by linear olefin feed occurs concurrentlywith the oligomerization of the olefin feed. Thus, the co-reactionresults in a mixture of oligomers (dimers, trimers, tetramers, etc.) andalkylated naphthalenes, including mono- and polyalkylated naphthalenes.The number of carbon atoms in the alkyl groups of the alkylatednaphthalenes will correspond to the number of carbon atoms in the linearolefin feed. Thus, the alkyl groups of the alkylated naphthalenes willhave from 10 to 24 carbon atoms.

Among the catalysts useful to effect these reactions are certainsilica-alumina clays, also called aluminosilicates. Silica-alumina claysprimarily are composed of silicon, aluminum, and oxygen, with minoramounts of magnesium and iron in some cases. Variations in the ratios ofthese constituents, and in their crystal lattice configurations, resultin some fifty separate clays, each with its own characteristicproperties.

One class of silica-alumina clays comprises smectite clays. Smectiteclays have a small particle size and unusual intercalation propertieswhich afford them a high surface area. Smectites comprise layered sheetsof octahedral sites between sheets of tetrahedral sites, where thedistance between the layers can be adjusted by swelling, using anappropriate solvent. Three-layered sheet-type smectites includemontmorillonites. The montmorillonite structure may be represented bythe following formula: ##EQU1## where M represents the interlamellar(balancing) cations, normally sodium or lithium; and x, y and n areintegers.

Montmorillonite clays may be acid-activated by such mineral acids assulfuric acid and hydrochloric acid. Mineral acids activatemontmorillonites by attacking and solubilizing structural cations in theoctahedral layers. This opens up the clay structure and increasessurface area. These acid-treated clays act as strong Bronsted acids.Applicants discovered that certain acid-treated montmorillonite claycatalysts are particularly effective for preparing synthetic lubricantbase stocks in good yield by oligomerizing long-chain olefins. Theseclays are acidic calcium montmorillonite clays having a moisture contentranging up to about 20 wt.%, a residual acidity in the range of about 3to about 30 mg KOH/g (when titrated to a phenolphthalein end point), anda surface area of about 300 M² /g or greater. Illustrative examplesinclude Filtrol grade 24, having a moisture content of 12 wt.%, aresidual acidity of 8.5 mg KOH/g, and a surface area of 425 M² /g;Filtrol grade 124, having a moisture content of 2 wt.%, a residualacidity of 7.0 mg KOH/g, and a surface area of 400 M² /g; Filtrol grade13, having a moisture content of 16 wt.%, a residual acidity of 15 mgKOH/g, and a surface area of 300 M² /g; Filtrol grade 113, having amoisture content of 4 wt.%, a residual acidity of 10 mg KOH/g, and asurface area of 300 M² /g; and Filtrol grade 224, having virtually nomoisture, and having a residual acidity of 3.0 mg KOH/g, and a surfacearea of 350 M² /g.

Preferably, the clay catalyst is activated by heat treatment beforerunning the co-reactions. Applicants have found that heat treatment ofthe catalyst prior to running an oligomerization reaction causes thecatalyst to be more active and produce a higher olefin conversion.Additionally, clays heat treated in this manner are more stable,remaining active during a reaction for a longer period of time. Theclays may be heat treated at temperatures in the range of about 50° to400° C., with or without the use of a vacuum. A more preferredtemperature range is 50° to 300° C. Optionally, an inert gas may be usedduring heat treatment as well. Preferably, the clay should be heattreated under conditions and for a length of time which will reduce thewater content of the clay to approximately 1 wt.% or less.

The oligomerization and alkylation co-reactions may be carried out ineither a stirred slurry reactor or in a fixed bed continuous flowreactor. The catalyst concentration should be sufficient to provide thedesired catalytic effect. The temperatures at which the oligomerizationand alkylation may be performed are between about 50° and 300 ° C., withthe preferred range being about 150° to 180 ° C. The reactions may berun at pressures of from 0 to 1000 psig.

Following the oligomerization and alkylation co-reactions, the alkylatednaphthalenes and partially unsaturated oligomers are completely reducedvia catalytic hydrogenation. Surprisingly, hydrogenation of thealkylated naphthalenes to alkylated Decalins results in a drop in thepour point of the resulting synthetic lubricant, with little or nonegative impact on other properties, such as viscosity index.Hydrogenation of the oligomers improves their thermal stability andhelps prevent oxidative degradation during the mixture's use as alubricant. The hydrogenation reaction for 1-decene oligomers may berepresented as follows: ##STR4## where n represents moles of monomerused to form the oligomer. The hydrogenation of a mono-alkylatednaphthalene may be represented as follows: ##STR5##

Hydrogenation processes known to those skilled in the art may be used. Anumber of metal catalysts are suitable for promoting the hydrogenationreaction, including nickel, platinum, palladium, copper, and Raneynickel. These metals may be supported on a variety of porous materialssuch as kieselguhr, alumina, or charcoal. A particularly preferredcatalyst for this hydrogenation is a nickel-copper-chromia catalystdescribed in U.S. Pat. No. 3,152,998, incorporated by reference herein.Other U.S. patents disclosing known hydrogenation procedures includeU.S. Pat. Nos. 4,045,508; 4,013,736; 3,997,622; and 3,997,621.

Unreacted monomer and naphthalene should be removed either prior to orafter the hydrogenation step. Optionally, unreacted monomer andnaphthalene may be stripped from the oligomers/alkylated naphthalenesprior to hydrogenation and recycled to the catalyst bed for co-reaction.The removal or recycle of unreacted monomer and naphthalene or, if afterhydrogenation, the removal of non-oligomerized alkane and non-alkylatedDecalin, should be conducted under mild conditions using vacuumdistillation procedures known to those skilled in the art. Distillationat temperatures exceeding 250 ° C. may cause the oligomers to break downin some fashion and come off as volatiles. Preferably, therefore, thereboiler or pot temperature should be kept at or under about 180 ° C.Procedures known by those skilled in the art to be alternatives tovacuum distillation also may be employed to separate unreactedcomponents from the oligomer/alkylated naphthalene mixture.

While it is known to include a distillation step after the hydrogenationprocedure to obtain products of various 100 ° C. viscosities, it ispreferred in the method of the present invention that no furtherdistillation (beyond removal of any unreacted monomer/linear alkane andnaphthalene/Decalin) be conducted. Thus, the method of this inventiondoes not require the costly, customary distillation step, yet,surprisingly, produces a synthetic lubricant component that hasexcellent properties and that performs in a superior fashion. However,in some contexts, one skilled in the art may find subsequentdistillation useful in the practice of this invention.

The invention will be further illustrated by the following-examples,which are given by way of illustration and not as limitations on thescope of this invention. The entire text of every patent, patentapplication or other reference mentioned above is hereby incorporatedherein by reference.

EXAMPLES Preparation of Oligomer/Alkylated Naphthalene Mixtures

Olefin, naphthalene, and clay catalyst were charged to a flask equippedwith a stirrer, thermometer, heating mantle, and water cooled condenser.A nitrogen purge was used. The mixture was vigorously stirred and heatedto the desired temperature for the desired period of time. An exothermwas observed with some olefin/naphthalene mixtures. At the end of thereaction, the mixture was cooled to ambient temperature, filtered withsuction, and the liquid analyzed by liquid chromatography. The resultsare shown in Table I. The presence of alkyl naphthalenes was confirmedby H₁ and C₁₃ -NMR. Unreacted monomer and naphthalene were then removedby vacuum distillation until a pot temperature of approximately 250 ° C.was reached (0.6 mm Hg).

Hydrogenation of Mixture to Alkylated Decalins/Reduced Oligomers

An autoclave was charged with nickel catalyst (10 g) and approximately200 g of the alkylated naphthalene and oligomer mixture prepared above(after unreacted monomer and naphthalene were removed). The autoclavewas then sealed and flushed three or four times with hydrogen. Theautoclave was then pressured to 1000 psig with hydrogen and heated to200 ° C. The mixture was stirred at this temperature for 4.0 hours. Theautoclave was repressured to 2000 psig as needed. The mixture was thencooled to ambient temperature, filtered and the properties determined onthe filtrate. The results are shown in Table II, below. C₁₃ and H₁ -NMRshowed that the naphthalenes had been reduced to Decalins.

                                      TABLE I                                     __________________________________________________________________________    REACTION OF NAPHTHALENE/OLEFIN MIXTURES WITH ACIDIC CLAYS                                    (g) of                                                                            Harshaw/         Time/ Con.(%),                                                                            Results from LC               Ex.            Reac-                                                                             Filtrol                                                                              (g) of    Temp  Naphthln/                                                                           M  D  T + D/T +               No.                                                                              Reactants   tants                                                                             Catalyst                                                                             Catalyst                                                                           Reactor                                                                            (Hr)/(°C.)                                                                   Olefin                                                                              (%)                                                                              (%)                                                                              (%) Ratio               __________________________________________________________________________    1  C-14A/Naphthalene                                                                          80/20                                                                            H/F Clay 113                                                                         10   Flask                                                                              6/160 >95/75                                                                              25.0                                                                             49.5                                                                             46.9                                                                              1.06                2  C-14A/Naphthalene                                                                         320/80                                                                            H/F Clay 113                                                                         40   Flask                                                                              5/160 98/75 25.0                                                                             41.6                                                                             55.0                                                                              0.76                3  C-14A/Naphthalene                                                                         360/40                                                                            H/F Clay 124                                                                         40   Flask                                                                              6/160   */92.3                                                                            7.76                                                                             28.8                                                                             63.6                                                                              0.45                4  C-14A/Naphthalene                                                                         380/20                                                                            H/F Clay 124                                                                         40   Flask                                                                              6/160   */88.8                                                                            11.2                                                                             36.1                                                                             52.7                                                                              0.69                5  C-14A/Naphthalene                                                                         320/80                                                                            H/F Clay 113                                                                         40   Flask                                                                              6/160   */87.7                                                                            18.4                                                                             46.0                                                                             35.6                                                                              1.29                6  C-14A/Naphthalene                                                                         320/80                                                                            H/F Clay 113                                                                         40   Flask                                                                              6/160   */86.0                                                                            14.0                                                                             36.5                                                                             49.5                                                                              0.74                7  C-14A/Naphthalene                                                                         320/80                                                                            H/F Clay 113                                                                         20   Flask                                                                              6/160   */80.6                                                                            19.4                                                                             45.1                                                                             35.5                                                                              1.27                8  C-14,16A/Naphthln                                                                         320/80                                                                            H/F Clay 13                                                                          40   Flask                                                                              6/160   */84.0                                                                            16.0                                                                             38.2                                                                             45.9                                                                              0.83                9  C-13,14I/Naphthln                                                                         320/80                                                                            H/F Clay 13                                                                          40   Flask                                                                              6/160   */85.2                                                                            14.8                                                                             37.4                                                                             47.8                                                                              0.78                10 C-15,18I/Naphthln                                                                         320/80                                                                            H/F Clay 13                                                                          40   Flask                                                                              6/160   */71.0                                                                            29.0                                                                             43.8                                                                             27.1                                                                              1.62                11 C-14A/Naphthalene                                                                         320/80                                                                            Dried H/F                                                                            40   Flask                                                                              5/140   */70.4                                                                            39.6                                                                             41.2                                                                             29.2                                                                              1.41                                   Clay 124                                                   12 C-14A/Naphthalene                                                                         320/80                                                                            Dried H/F                                                                            40   Flask                                                                              4/180   */82.2                                                                            17.8                                                                             40.0                                                                             42.2                                                                              0.95                                   Clay 124                                                   13 C-14A/Naphthalene                                                                         396/4                                                                             Dried H/F                                                                            40   Flask                                                                              5/160   */71.4                                                                            28.6                                                                             42.4                                                                             29.0                                                                              1.46                                   Clay 124                                                   __________________________________________________________________________     Con. = Conversion; M = Monomer; D = Dimer; T + = Trimer + Tetramer +          Pentamer, etc.; A = Alpha; I = Internal; * = not determined.             

                                      TABLE II                                    __________________________________________________________________________    IMPROVED PROPERTIES OF ALKYLATED DECALINS/REDUCED                             OLIGOMERS MIXTURES                                                                              Properties Before/After Hydrogenation                       Ex.                                                                              Mixture Prepared as Recorded                                                                 % Remaining                                                                          VIS (cSt)  Pour Point                                No.                                                                              in Table I     by TGA @ 210° F.                                                                    VI   (°F.)                              __________________________________________________________________________    1  C-14A Olig/Alkyl Nap                                                                         94.8/93.2                                                                            12.3/12.8                                                                           110/110                                                                            -30/-35                                   2  C-14A Olig/Alkyl Nap                                                                         93.5/93.5                                                                            10.3/10.5                                                                           120/120                                                                            -25/-35                                   3  C-14A Olig/Alkyl Nap                                                                         89.2/89.2                                                                            7.61/7.92                                                                           143/121                                                                            -30/-35                                   4  C-14A Olig/Alkyl Nap                                                                         *      4.76/5.04                                                                           133/126                                                                            -25/-30                                   5  C-14A Olig/Alkyl Nap                                                                         *      13.3/13.4                                                                           111/106                                                                            -25/-35                                   6  C-14A Olig/Alkyl Nap                                                                         95.8/95.8                                                                            12.9/12.4                                                                           110/105                                                                            -30/-35                                   7  C-14A Olig/Alkyl Nap                                                                         97.2/* 9.84/10.1                                                                           108/106                                                                            -30/-35                                   8  C-14,16A Olig/Alkyl Nap                                                                      86.0/* 12.8/13.1                                                                           110/112                                                                            -20/-40                                   9  C-13,14I Olig/Alkyl Nap                                                                      96.4/* 12.4/12.8                                                                           106/104                                                                            -40/-30                                   10 C-15,18I Olig/Alkyl Nap                                                                      96.6/* 11.7/12.3                                                                           107/108                                                                             -15/<-50                                 11 C-14A Olig/Alkyl Nap                                                                         96.2/* 9.06/9.69                                                                           114/114                                                                            -25/-25                                   12 C-14A Olig/Alkyl Nap                                                                         *      11.1/12.1                                                                           106/110                                                                            -25/-35                                   13 C-14A Olig/Alkyl Nap                                                                         *      5.59/*                                                                              139/*                                                                              -20/*                                     __________________________________________________________________________     A = Alpha; I = Internal; Alkyl Nap = Alkylated Naphthalenes; Olig =           Oligomers; * = not determined.                                           

We claim:
 1. A synthetic lubricant base stock having a low pour point,comprising a mixture of (1) reduced oligomers prepared from a linearolefin having from 10 to 24 carbon atoms; and (2) alkylated decalinhaving an alkyl group containing from 10 to 24 carbon atoms.
 2. Thesynthetic lubricant base stock of claim 1, wherein the mixture containsfrom about 1 to about 80 wt.% alkylated decalin.
 3. The syntheticlubricant base stock of claim 1, wherein the mixture contains from about5 to about 40 wt.% alkylated decalin.
 4. The synthetic lubricant basestock of claim 1, wherein the reduced oligomers and alkylated decalincomprise hydrogenated co-reaction products of a linear olefin havingfrom 10 to 24 carbon atoms and naphthalene.
 5. The synthetic lubricantbase stock of claim 1, wherein the mixture has a pour point of less thanabout -35 ° F.
 6. A synthetic lubricant base stock having a low pourpoint, comprising a mixture of (1) oligomers prepared from a linearolefin having from 12 to 18 carbon atoms; and (2) alkylated decalinhaving an alkyl group containing from 12 to 18 carbon atoms, wherein themixture contains from about 5 to about 40 wt.% of said alkylateddecalin.
 7. The synthetic lubricant base stock of claim 6, wherein theoligomers and alkylated decalin comprise hydrogenated co-reactionproducts of a linear olefin having from 12 to 18 carbon atoms andnaphthalene.
 8. A process for preparing synthetic lubricant base stockshaving a low pour point, comprising the steps of (1) co-reactingnaphthalene and a linear olefin having from 10 to 24 carbon atoms in thepresence of an acidic montmorillonite clay; and (2) hydrogenating themixture resulting from step (1), to obtain a mixture comprising reducedolefin oligomers and alkylated decalins.
 9. The process of claim 8,wherein the naphthalene and linear olefin of step (1) are co-reacted ina weight ratio of naphthalene to linear olefin of about 1:99 to about2:3.
 10. The process of claim 8, wherein the naphthalene and linearolefin of step (1) are co-reacted in a weight ratio of naphthalene tolinear olefin of about 1:20 to about 1:4.
 11. The process of claim 8,wherein the linear olefin of step (1) has from 12 to 18 carbon atoms.12. The process of claim 8, further comprising the step of (3) removingfrom the mixture resulting from step (2) any non-oligomerized alkane andnon-alkylated decalin.
 13. A process for preparing synthetic lubricantbase stocks having a low pour point, comprising the steps of (1)co-reacting naphthalene and a linear olefin having from 10 to 24 carbonatoms in the presence of an acidic montmorillonite clay; and (2)removing from the mixture resulting from step (1) any non-oligomerizedlinear olefin and non-alkylated naphthalene; and (3) hydrogenating themixture resulting from step (2), to obtain a mixture of reduced olefinoligomers and alkylated decalins.
 14. The process of claim 13, whereinthe naphthalene and linear olefin of step (1) are co-reacted in a weightratio of naphthalene to linear olefin of about 1:99 to about 2:3. 15.The process of claim 13, wherein the naphthalene and linear olefin ofstep (1) are co-reacted in a weight ratio of naphthalene to linearolefin of about 1:20 to about 1:4.
 16. The process of claim 13, whereinthe linear olefin of step (1) has from 12 to 18 carbon atoms.
 17. Theprocess of claim 13, wherein the non-oligomerized linear olefin andnon-alkylated naphthalene removed in step (2) are recycled andco-reacted as in step (1).